1. Field of the Invention
The present invention relates to a trolley and, more particularly, to a positioning device of telescopically retractable vertical bars of a trolley.
2. Description of Related Art
Retractable trolleys are known to comprise a pair of telescopically retractable vertical bars forming components of a frame, a positioning device for positioning the retractable vertical bars, a handle bar connecting the vertical bars, a supporting seat for carrying baggage and a wheel assembly. A typical structure of conventional positioning devices of the retractable vertical bars comprises a hole defined in a periphery tube wall of an inner tube of the vertical bars, a latch biased by a resilient member which in turn is connected to a control device to operably engage/disengage the latch from the hole to thereby locking/unlocking the vertical bars in position. In order to be used with various heights, a number of holes are usually provided in the periphery wall along an axial direction of the inner tube.
Although more holes provided in the inner tube means more flexible use of the trolley, punching holes in a tube wall is however a destructive design and will eventually weaken the structural strength of the entire trolley. Further, no matter how many holes are provided, it is still a step-adjusting design rather than a continuous smooth positioning design.
The present invention provides an improved positioning device to mitigate and/or obviate the aforementioned problems.